ARRANGEMENT OF STRUCTURAL ELEMENTS. 211 



more on the development of a group of central cells 

 than on that of either of the other groups mentioned. 

 There is, however, another and more formal way in 

 which the structure of the central system can be pre- 

 sented. For the original description of this plan we are 

 indebted to the Viennese anatomist, Meynert. 1 He 

 looked upon the central nervous system as composed of 

 three principal masses of grey matter namely, the 

 cortex of the hemispheres, the basal ganglia, and the 

 central grey matter of the cord. (See Fig. 41.) 



The fibres which connect the cortex (C) with the 

 basal ganglia (L and 5) form Meynert's projection 

 system of the first order ; those uniting the basal 

 ganglia with the central grey matter of the cord, that of 

 the second order ; while the fibres (D.r. and V.r.) uniting 

 the central grey matter of the cord with the periphery 

 form the system of the third order. In addition, he dis- 

 tinguished two other systems of fibres within each prin- 

 cipal subdivision of the central system : the commissural 

 (c c\ which connects symmetrical points on opposite 

 sides of the median plane ; and the associational (a), 

 which connects points on the same side. An abundance 

 of objections can be urged against the details of this 

 scheme, and even some of the fundamental points which 

 it was intended to illustrate must be abandoned, but it 

 had in its time the value of a good working hypothesis. 

 Applying to it the notion of the construction of the 

 central system which I think more hopeful, it appears 

 that the projection system of the third order includes 

 our group of afferent and efferent fibres, and that the 

 remnant of the scheme represents details of arrange- 

 ment among the central cells, details which are most 

 highly elaborated in the encephalon. The relations of 



1 Meynert, in $tricker's Handbuch d.er Lckrc von den 

 1872. 



